A coupling is shown in DE 25 40 191 C3. The coupling includes a power drive in the form of a double-acting hydraulic cylinder with a circular-ring-shaped cylinder chamber. An actuating element, in the form of a disc, is axially adjustable by the hydraulic cylinder. When the actuating element is in position so that the friction assembly is transferred into its torque transmitting position, a plate spring is pretensioned between the friction assembly and the actuating element. A hydraulic pulse is released to transfer the actuating element into the switched-on position. After the switched-on position has been reached, the hydraulic pressure in the hydraulic cylinder drops. The actuating element is held in the switched-on position by an engaging device. The coupling is opened in the opposite direction by loading the double-acting hydraulic cylinder. However, a disadvantage is that, when the actuating element is transferred towards the switched-on position by the hydraulic cylinder, the hydraulic cylinder moves the actuating element beyond the switched-on position in the direction of the friction assembly. Thus, only after the hydraulic pressure has dropped, is the final switched-on position reached while a predetermined torque of the friction assembly is set. Furthermore, the coupling cannot be used in applications where the coupling has to be switched off when the pressure in the hydraulic system drops. Furthermore, the circular-ring-shaped cylinder chamber requires a high pressure to be able to displace the actuating element.